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https://issues.apache.org/jira/browse/FLINK-21817?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17313346#comment-17313346
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Stephan Ewen commented on FLINK-21817:
--------------------------------------

Fixed in 1.13.0 via 
  - 65b43c45c69c20a51f2926d29be46c779fe65af
  - 2be15338c00e75361566fe3010091ea61f0af645

> New Kafka Source might break subtask and split assignment upon rescale
> ----------------------------------------------------------------------
>
>                 Key: FLINK-21817
>                 URL: https://issues.apache.org/jira/browse/FLINK-21817
>             Project: Flink
>          Issue Type: Bug
>          Components: Connectors / Common
>    Affects Versions: 1.12.2
>            Reporter: Kezhu Wang
>            Assignee: Qingsheng Ren
>            Priority: Blocker
>              Labels: pull-request-available
>             Fix For: 1.13.0, 1.12.3
>
>
> On restoring, splits are add back directly to {{SourceReader}} in 
> {{SourceOperator}}. In no rescaled restoring, bindings between splits and 
> subtasks are preserved due to no repartition in 
> {{RoundRobinOperatorStateRepartitioner}}. But in rescaled restoring, these 
> operator states will be redistributed cross existing subtasks. This might 
> break possible assignment from {{SourceEnumerator}}.
> Given {{KafkaSource}} as an example, the partition to subtask assignment is 
> decided by {{KafkaSourceEnumerator.getSplitOwner}}. The mappings will break 
> after rescaling.
> I pushed [a test 
> case|https://github.com/kezhuw/flink/commit/9dc13cd9d7355d468a6ac8aae1b14b3a267581b6#diff-ad6e86c3757199ac3247687a71f9c34ee67b9ac743ae88a9f660950f27bec6eeR238]
>  using {{KafkaSource}} for evaluation.
> I think it requires api addition to solve in generic and configurable way.
> Is it a valid issue ? I am not that sure.
> cc  [~jqin] [~sewen]



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